The long term goal of this application is to improve our understanding of the properties of the cortical cell cytomatrix and of its pleiotropic functions in a variety of processes, including exo-endocytosis, cell adhesion and cell proliferation. More specifically, this application will focus on specialized cellular compartments, primarily the neuronal synapse and the podosome rosettes of v-Src-transformed cells, as model systems to investigate fundamental questions in this area, such as the mechanisms that anchor cytoskeletal scaffolds to the membrane, the role of these scaffolds in membrane deformation and the regulation of actin at sites of cell adhesion. Several aims will be pursued. 1) Further characterization of neuronal amphiphysin as a regulated adaptor between the membrane bilayer, endocytic coats and the actin based cytoskeleton of endocytic zones of synapses (also called "periactive zones", because they surround the active zones of secretion). 2) Identification of mechanisms underlying the regulation of actin dynamics at synaptic endocytic zones, with emphasis on the role of the Rac specific guanylnucleotide exchange factor (GEF) Tiam (Still-life), of a novel putative Rho family GEF which shares blocks of amino acid similarity with amphiphysin, and of a newly discovered interaction between talin and a PI(4) 5-kinase. 3) Elucidation of the function at sites of cell adhesion of protein families which participate in synaptic vesicle endocytosis at periactive zones of synapses. These include dynamin, amphiphysin and endophilin. This line of research will follow-up the observation of striking morphological and biochemical similarities between synaptic periactive zones and the actin-based scaffolds at cell-substrate contact sites (podosome rosettes) in cells with high levels of Src activity. We anticipate that these studies will have important implications for the cancer field. Podosome/invadopodia mediate cell migration of transformed cells and tissue invasion. Tiam was first identified as a protein required for metastatic invasion, amphiphysin was found to be abnormally expressed in breast cancer and several synaptic proteins are members of tumor suppressor families.